Subfield code $8 - Field link and sequence number (R ) (Appendix A: Control Subfields )
Subfield $8 contains data that identifies linked fields and may also propose a sequence for the linked fields. Subfield $8 may be repeated to link a field to more than one other group of fields. The structure and syntax for the field link and sequence number subfield is:
$8<linking number>.<sequence number>\<field link type>
The linking number is the first data element in the subfield and required if the subfield is used. It is a variable-length whole number that occurs in subfield $8 in all fields that are to be linked. Fields with the same linking number are considered linked.
The sequence number is separated from the linking number by a period ( . ) and is optional. It is a variable-length whole number that may be used to indicate the relative order for display of the linked fields (lower sequence numbers displaying before higher ones). If it is used it must occur in $8 subfields containing the same linking number.
The field link type is separated from preceding data by a reverse slash ( \ ). It is a code indicating the reason for the link and it follows the link number, or sequence number if present. Field link type is required except when subfield $8 is used to link and sequence 85X-87X holdings fields. The following one-character field link type codes have been defined in MARC for use in subfield $8:
c - Constituent item
Code c is used in a record for a collection, or a single item consisting of identifiable constituent units, to link the fields relating to the constituent units. All other non-linked data elements in the record pertain to the collection or item as a whole.
Example:
245 10$aBrevard Music Center$nProgram #24$h[sound recording].
505 0#$aFrom my window / Siegmesiter (world premiere) - Don Giovanni. Il mio tesorof [i.e. tesoro] / Mozart - Martha. M'appari / Flotow - Turandot. Nessun dorma / Puccini - Pines of Rome / Respighi.
650 #0$81\c$aSuites (Orchestra), Arranged.
650 #0$82\c$83\c$84\c$aOperas$xExcerpts.
650 $0$85\c$aSymphonic poems.
700 1#$82\c$84\c$aDi Giuseppe, Enrico,$d1938-$4prf
700 12$81\c$aSiegmeister, Elie,$d1909-$tFrom my window;$oarr.
700 12$82\c$aMozart, Wolfgang Amadeus,$d1756-1791$tDon Giovanni$pMio tesoro.
700 12$83\c$aFlotow, Friedrich von,$d1812-1883$tMartha.$pAch! So fromm, ach! so traut.$lItalian
700 12$84\c$aPuccini, Giacomo,$d1858-1924$tTurandot.$pNessun dorma.
700 12$85\c$aRespighi, Ottorino,$d1879-1936$tPini di Roma.
r - Reproduction
Code r is used in a record for a reproduction to identify fields linked because they contain information concerning only the reproduction. Other descriptive information in the record pertains to the original [with the exception of field 007 (Physical Description Fixed Field), 008 (Fixed-Length Data Elements: Books, Music, Serials, or Mixed Material positions 23 (Form of item)), field 245 subfield $h (Title Statement / Medium), and field 533 (Reproduction Note)].
Example:
007 <microform>
008/23 a (Microfilm)
245 04$aThe New-York mirror, and ladies' literary gazette$h[microform]
533 ##$aMicrofilm$bAnn Arbor, Mich. :$cUniversity Microfilms,$d1950.$e3 microfilm reels ; 35 mm.$f(American periodical series, 1800-1850 : 164-165, 785)
830 #0$84\r$aAmerican periodical series, 1800-1850 ;$v164-165, 785.
To return:
Use the 
key.
See also:
